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Injection vs Carb

Mconner7

Well Known Member
I have an O-540 A4D5 on my -10. I am considering the idea of upgrading to fuel injection. Is the efficiency worth the expense (~$5k) or should I keep it simple?
 
If it really costs 5G the payback will take a while, for sure. I’m sure you saw the parts listed in the classifieds, perhaps you can get the job done for less. There is a real satisfaction though to being able to go lean of peak with no change in engine smoothness. Like a constant speed prop, once you switch to fuel injection you won’t be interested in going back.
 
Might be a bit more than that depending on what you have now concerning your electrical system.
Electronic fuel injection needs a constantly running electric fuel pump and that one consumes quite some power, meaning you are going to need a second source for that kind of power.
I am putting in two EarthX batteries and two alternators to have full redundancy.
 
Might be a bit more than that depending on what you have now concerning your electrical system.
Electronic fuel injection needs a constantly running electric fuel pump and that one consumes quite some power, meaning you are going to need a second source for that kind of power.
I am putting in two EarthX batteries and two alternators to have full redundancy.



Not going electronic, just wondering if hard starts and some money spent is worth upgrading.
 
With injection, running lean of peak in cruise you save 20-30% of fuel for only a 5% reduction in speed. Depending how you fly the additional range may be worth something that a "payback" doesn't account for.

As far as the hard starts go, get a 6 cylinder P-Mag and you won't have hard starts. With two slick mags the hard starts existed for me, slapped on a P-Mag and now it starts within a few blades after a quick fuel stop.

Given a choice I won't own a carb again.
 
I have an O-540 A4D5 on my -10. I am considering the idea of upgrading to fuel injection. Is the efficiency worth the expense (~$5k) or should I keep it simple?

What's your fuel burn at various power settings? If you share that, someone can give you a rough idea of how much fuel you might save with injection.

Of course, you will add the complexity and hot start issues also associated with fuel injection.
 
What kind of injection would that be?

With injection, running lean of peak in cruise you save 20-30% of fuel for only a 5% reduction in speed
Maybe you meant to say "save 2 to 3%??" over a carbed engine?
That would be somewhat accurate and more realistic and perhaps a 5kt speed reduction if you are able to run on the extreme side of LOP or about 10.5 gph.

I certainly would not trade my IO-540 for an O-540 but fuel savings would not be motivating enough for me to consider an upgrade, especially if I already owned a perfectly well running carbureted version.
You'll be down for a considerable amount of time to upgrade all the necessary IO components, like high pressure mechanical fuel pump, high pressure boost pump, etc.
If you go down the rabbit hole of adding a new electronic ignition, pmag or other, you'll spend closer to $10,000.
If you saved a gallon per hour <8%> highly unlikely, it would take you over 1400 hrs to break even.
 
Maybe you meant to say "save 2 to 3%??" over a carbed engine?
That would be somewhat accurate and more realistic and perhaps a 5kt speed reduction if you are able to run on the extreme side of LOP or about 10.5 gph. Snip

I assume similar fuel burn for similar power settings for carb vs injection. I see 20-30% fuel savings (fuel burned vs distance traveled) by running 25 degrees LOP vs. ROP. N7ZK saves 2.5-3 GPH (altitude varies) LOP burning 9.5-11.5 an hour. Knotical mile per gallon is what I am talking about, or efficiency and range. LOP it loses 5-8 knots so the time penalty is minimal.

Will spending the time and money to upgrade to fuel injection payback like a business investment, probably not but it might help you erase a fuel stop from a trip.

With one P-mag the hot start issue is non existent.
 
Maybe you meant to say "save 2 to 3%??" over a carbed engine?
That would be somewhat accurate and more realistic and perhaps a 5kt speed reduction if you are able to run on the extreme side of LOP or about 10.5 gph.

I certainly would not trade my IO-540 for an O-540 but fuel savings would not be motivating enough for me to consider an upgrade, especially if I already owned a perfectly well running carbureted version.
You'll be down for a considerable amount of time to upgrade all the necessary IO components, like high pressure mechanical fuel pump, high pressure boost pump, etc.
If you go down the rabbit hole of adding a new electronic ignition, pmag or other, you'll spend closer to $10,000.
If you saved a gallon per hour <8%> highly unlikely, it would take you over 1400 hrs to break even.

The previous poster is correct. Going from best power (80 ROP) to max MPG lean (20 LOP) nets at least a 20% reduction in fuel burn for only about a 5-7% power reduction. Most carb'ed engines can't get there. The 10 is a bit unique, as it is over powered for those looking for fuel efficiency. I fly well under 65% and going 50-100* LOP is more efficient than running peak and pulling the throttle back, at least it is with an optimized advance table. If the OP is runs at higher speeds where Peak or richer is a good thing, then savings are less. Balanced injectors can save .5-1.5 GPH over stock FI on a 540, let alone a carb's poor distribution. On my 320, I was able to reach the same speeds at 1 GPH less after pulling the carb and installing FI, not counting the savings of running LOP, which I couldn't do with the carb.

In my 10 at 8-10K I get a very reliable 165 KTAS at 10.5 GPH. At 14K it is around 9.2. That is with FI, balanced injectors and pilot adjustable ignition advance.

All that said, if you are buying all new off the shelf stuff at today's prices, I agree that it is a LONG payback period.

Larry
 
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I have an O-540 A4D5 on my -10. I am considering the idea of upgrading to fuel injection. Is the efficiency worth the expense (~$5k) or should I keep it simple?

The efficiency gains of moving to FI are only partially realized unless you have a means to optimize your ignition curve for LOP ops. Mechanical FI gets you a little; adding an EI with a cookie cutter curve gets you a little more; but installing a fully adjustable EI from SDS along with an optimized curve and tuned nozzles gets you about as good as you can get with a SI engine.

The "Full Monty" of course is the SDS EFI.

If you are looking for a way to dip your toe in the water, the best bang for the buck you can do right now is buy a single CPI ignition. You can do one side for about a grand and will lay the foundation for the future. The old saw about "the first EI gets you 70% of the benefit of dual EI" is true - but only if you are discussing the typical EI with a pre programmed curve. Choosing SDS allows you to optimize that one EI to "almost" eliminate the need for the second (from an engine efficiency standpoint).

Spend a few bucks and buy the CPI, tune it for the best LOP ops the carb delivers and see what happens. If you are still trying to eke out some more efficiency, look to FI as the next step.
 
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The efficiency gains of moving to FI are only partially realized unless you have a means to optimize your ignition curve for LOP ops. Mechanical FI gets you a little; adding an EI with a cookie cutter curve gets you a little more; but installing a fully adjustable EI from SDS along with an optimized curve and tuned nozzles gets you about as good as you can get with a SI engine.

The "Full Monty" of course is the SDS EFI.

If you are looking for a way to dip your toe in the water, the best bang for the buck you can do right now is buy a single CPI ignition. You can do one side for about a grand and will lay the foundation for the future. The old saw about "the first EI gets you 70% of the benefit of dual EI" is true - but only if you are discussing the typical EI with a pre programmed curve. Choosing SDS allows you to optimize that one EI to "almost" eliminate the need for the second (from an engine efficiency standpoint).

Spend a few bucks and buy the CPI, tune it for the best LOP ops the carb delivers and see what happens. If you are still trying to eke out some more efficiency, look to FI as the next step.

I have to disagree. If the objective is cruise engine efficiency, the 99% solution, the one that has the least impact (as in cost, complexity and not having an engine dependent on ship's power) is standard fuel injection with balanced injectors and dual pMags.

While I can see some marginal gain in tweaking ignitions timing for each area of operation, I suspect few do this. 20 years of flying pMag tells me that if operated with the jumper in most engines are close to optimal.

Balanced injectors typically require ~3 data runs and replacing 1 or up to 4 injector nozzles - ~$26 each from AirFlow Performance (they fit the stock Lycoming injectors as well)

Before I got the first set of pMags I ran an EI that did allow for in flight timing changes. Never found it to do anything worthwhile - other than having multiple failures. It got pulled at 300 hours.

I also note for the RV-10, the six cylinder pMag allows for the pilot to select a fixed base engine timing or a timing based on RPM and MP, and do so in flight. For the standard IO-540 I use 25 as the base and a max advance of 34 degrees.

Carl
 
In my 10 at 8-10K I get a very reliable 165 KTAS at 10.5 GPH.
That is my experience as well.
But to validate a 20 to 30% reduction over a carbed version, I want to know what your experience shows for comparison or do you just assume a number to make the savings look real good?
Maybe the OP could post some numbers based on his O-540 installation?

We could split the assumption and take 25% fuel savings.
That would mean that a carbed version burns 14gph x .25% reduction=3.5gallons. Now you are at 10.5 gph.

Throwing in all kinds of other enhancements will result in additional savings but
the OP was interested in what could be gained by changing his carbed version to an injected version.
 
I have many years of Pmag flying and many years of SDS. Significant formal flight test shows me that optimized timing offered by the SDS is a game changer.

I'm happy to compare your data with mine.
 
The fuel savings and efficiency gains with the SDS are real. I'll post my numbers right up there with Toolbuilder for comparison, in my 9A with IO360. I fly too many hours each year behind SDS to listen to people say "it ain't real"....

My -10 kit ships in October, and yes it will get "The Full Monty".
 

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That is my experience as well.
But to validate a 20 to 30% reduction over a carbed version, I want to know what your experience shows for comparison or do you just assume a number to make the savings look real good?
Maybe the OP could post some numbers based on his O-540 installation?

We could split the assumption and take 25% fuel savings.
That would mean that a carbed version burns 14gph x .25% reduction=3.5gallons. Now you are at 10.5 gph.
Snip

The 20-30% fuel savings has no assumptions. It is comparing running LOP vs ROP with the same injected RV-10.

This gives the OP a data set to contemplate: Fly LOP at 5-8 knots slower burning 2.5-3 GPH less (out of 13 GPH) vs keep blowing gas out the exhaust with the carbed engine and fly a little faster.

Adding a P-mag (or other variable ignition) is not necessary but does serve to eases the hot starts and in the case of the P-Mag saves about 0.5 GPH.
 
Always cracks me up that these old wives tales persist. Yes, going LOP can give a sag in speed. And since the past experience with LOP ops in GA was predominantly fixed timing magnetos, the sag in speed became "the truth". But the reality is that tuned injectors brings some of that speed back, and variable timing brings back more. Those are more recent "New Truths". Many people are happy with the "new truth" and cant imagine anything better.

But as I have illustrated many times on this forum, there is an even "Newer Truth". And that is a timing curve optimized for ROP and LOP ops. Even with the same RPM and MAP, the flame speed is very different between the two conditions. This different flame speed drives a different advance number. This is fact. And the difference in performance on a PV lycoming is startling. P-mag owners dont get to see this change in performance because there is no option to switch back and forth between the two values, but once you see it, its as obvious as a slap across the face.

This thread is specifically looking for injection vs carb benefits, but the answer is more nuanced then that.
 
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Still waiting

I am still waiting to hear what a carbed O-540 will burn, leaned out and doing 165kts in an RV-10 between 8000 and 11,000 feet. Some real data, from the OP and for arguments sake let's keep the other enhancements out of it.
The OP asked a simple question,

I have an O-540 A4D5 on my -10. I am considering the idea of upgrading to fuel injection. Is the efficiency worth the expense (~$5k) or should I keep it simple?

I am well aware of electronic ignition improving fuel efficiency allowing LOP operation but I would like to know, just like the OP,
is the efficiency of a fuel injected system worth the expense???
How much more efficient? Injected vs carbed, no other changes.
 
Yes, the answer to the OPs question, which no one knows, depends on his current situation: How lean can he cruise with his current carb set up?
 
No experience with the O/IO 540 but as per the Lycoming Operators Manual there is little difference in fuel consumption between an O/IO 320 when leaned for economy fuel flows.

In my experience a carb O 320 leaned to roughness and then enriched to just acceptably smooth will have individual cylinders range from just ROP to LOP which would give fuel flows slightly above an injected engine at LOP.

The 9A with the best confirmed fuel economy figures I have seen on VAF has a carb.

Fin
9A
 
The 20-30% fuel savings has no assumptions. It is comparing running LOP vs ROP with the same injected RV-10.

This gives the OP a data set to contemplate: Fly LOP at 5-8 knots slower burning 2.5-3 GPH less (out of 13 GPH) vs keep blowing gas out the exhaust with the carbed engine and fly a little faster.

A bit of math and the performance charts show that most or all of that saving is from flying slower and leaning from best power to best economy.

The LOP proponents have convinced people that operating your engine the way the designer intended is dangerous. I don't believe that.

Here's a better test:
Set your baseline as LOP - measure speed and GPH.

Return to ROP, then lean to best economy as per the engine manual and adjust the throttle to give you the same speed as LOP.

That will show you the savings you get from LOP. It won't be 20%. My guess is 2-3%, if you can measure that accurately.
 
Here are my numbers

I tried to reply to share my numbers…just landed from an 1100 NM trip.

Economy cruise at 15,000’ 14”/2300 9 gph at 155 TAS

Normal cruise at 14,500 19”/2400 163 TAS 10.3 gph

Lower altitude leg, 10,500’ 21”/2300 162 TAS 10.5 gph

If I crack the carb heat, I can get all EGT’s within 25 degrees and run 75 degrees LOP.
 
I rest my case!

I see that you are a working man, just like most of us.
Those are great numbers and hard to beat with fuel injection.
It appears that I may have been too generous in assuming a fuel saving of 2 to 3%, perhaps a slight loss or dead even.

There are many advantages to an injected engine especially in conjunction with electronic ignition systems but claiming 20 to 30% reduction in fuel consumption is simply not true.

Below is a snippet out of the Lycoming operators manual.

Induction System – Lycoming O-540 series engines are equipped with a Marvel-Schebler MA-4-5 carburetor. Particularly good distribution of the fuel-air mixture to each cylinder is obtained through the center zone induction system, which is integral with the oil sump and is submerged in oil, insuring a more uniform vaporization of fuel and aiding in cooling the oil in the sump. From the riser the fuel-air mixture is distributed to each cylinder by individual intake pipes.
 
Mark, are these numbers knots? If so, your carb is doing very well.

I tried to reply to share my numbers…just landed from an 1100 NM trip.

Economy cruise at 15,000’ 14”/2300 9 gph at 155 TAS

Normal cruise at 14,500 19”/2400 163 TAS 10.3 gph

Lower altitude leg, 10,500’ 21”/2300 162 TAS 10.5 gph

If I crack the carb heat, I can get all EGT’s within 25 degrees and run 75 degrees LOP.
 
Mark, are these numbers knots? If so, your carb is doing very well.

Yes speeds are in knots. I took a friend who has FI yesterday and he agreed that about the only gain would be smoother LOP running. I have one SureFly SIM that helped a lot but it is not smooth at the LOP i listed. I usually run close to peak and give up 1/2-1 gph.
 
There are many advantages to an injected engine especially in conjunction with electronic ignition systems but claiming 20 to 30% reduction in fuel consumption is simply not true.

For the record, I never claimed that. I said that going from 80 ROP to 20 LOP would reduce speed by 5-7% and reduce FF by 20-30%. Clearly Mconnor is lucky with his setup, as on my 320 I could not get that lean, so I saved a full GPH at similar speeds once I did the FI upgrade plus the improved fuel balancing. I do see benefits to adjustable advance and balanced injectors. For example, Mconnor got 163 Ktas and 10.3 at 15K. I routinely fly 14K at 165 Ktas and get around 9.2 GPH. That is a 10% reduction. So there are benefits to be had. At higher altitudes, I need to be closer to peak to keep the 165 knots and therefore retard timing a good bit compared to where I would be at 10K. If I ran off the typical advance maps, I would be WAY too advanced, as the advance keeps growing as the MAP drops. This is the beauty of pilot controlled advance. You set whatever timing is appropriate for the given set of circumstances. No need to be an engine guru. Just change the advance, wait 60 seconds and observer airspeed. Repeat until highest TAS is achieved. At 165 KTAS, I can make the airspeed move +/- 5 knots by twisting the knob; More if I got extreme with it.
 
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Yes speeds are in knots. I took a friend who has FI yesterday and he agreed that about the only gain would be smoother LOP running. I have one SureFly SIM that helped a lot but it is not smooth at the LOP i listed. I usually run close to peak and give up 1/2-1 gph.

Since you run LOP and high altitude, I can tell you with certainty that the Surefly is leaving performance on the table. Switch to SDS CPI, spend 5 minutes finding the optimized timing for your typical cruise condition, and you will pick up 3 knots minimum.

Is 3+ knots worth a thousand bucks in hardware and a weekend of work?
 
I agree

That would be an interesting combination and one we don't have much data on.
Not too many O-540s in RV-10s and having a carbed version with good numbers such as the OP stated is pretty rare.
This would give us some real numbers to compare against the predominately injected installations.
Yes, why not install a Surefly (or other) in place of one of the mags before contemplating a switch to injection??
 
Emags or SDS EFI

I am building RV 10, I have Lycoming Thunderbolt YIO-540-D4A5 engine, Hartzell C2YR-1 BFP/F8068D prop and Emags, all to be installed.
I wish to know advantages/disadvantages of SDS EFI compared to Emags
Thanks
 
Im guessing that you are actually discussing the SDS and Emag ignition products, because SDS EFI gives you a fuel system AND an ignition system. The Pmag is ignition only. Two different worlds.

Advantages of CPI over Pmag:

-More mechanically and electronically robust (no moving parts, no wear items, no inspection requirements, electronics not installed on the hot side of the firewall, better protected from environmentla factors)
-Better real world performance ROP and LOP
-lighter
-less expensive
-built in engine parameter display (timing, voltage, MP, tach, etc)
-fully configurable in cockpit/in flight (no need for third party display or mechanical "spoofing" timing to get what you want)

Advatage of Pmag over CPI:
-Ease of initial installation

If you are in fact considering Emags "OR" the full monty SDS EFI, that is a longer discussion. But as luck would have it, I also have quite a bit of first hand experience.
 
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